Does anyone know the legality of getting desktop PCs onto planes, assuming they respect the dimension and weight limits?

I travel a lot and I want to build a portable mITX that I can take on international flights, but I'm skeptical about them letting me bring it on planes.

I originally was looking to build my own briefcase PC, which for those who don't know is basically just a chubby laptop without a battery built into a carrying case, but there's no way I can make something like that without it looking like Achmed's clock.

I was thinking maybe the Lian-Li PC-TU100A, or something else with a handle and easy-release side panels so I can show curious TSA inspectors what's inside it.